ON ACTING: The Actor's Skill

I was reading a series of Mystery Writer's of America short stories, and came upon a quote from Eric Ambler concerning liars, and I thought it might apply equally as well to good actors.

All words between [ ] are mine:

"Now the only thing that makes a liar [the way the general public perceives an actor] tolerable is innocence. No matter how outrageous the fairy tale [scene or story], she or he [the actor] must believe it at the time.The game of make-believe is then possible. The rules are tacitly accepted by both parties [the actor and the audience]. The element of calculation is almost non-existent. To find, suddenly, then, that not merely has all the make-believe been on your [the audience's] side, but that you have been listening like a fool to someone [the actor] skillfully pretending [?] to be a pathological liar, is a shattering experience. What sort of mind is it that can contrive such a disguise? And what is it that has to be hidden?"